The present invention relates to forming elements and apparatus and particularly to such elements and apparatus employed in casting cementitious material as an invert or trough in a manhole or the like.
In the conventional construction of pipeline systems for sewage and storm drainage and the like, manholes of the form of an upright tubular housing are located at strategic points in the pipeline network to provide access thereto for maintenance, repair and similar activities, manholes being typically located at periodic spacings along linear sections of pipeline and at the junction of two or more pipeline sections. In the normal manhole construction, the manhole housing is formed with openings at its lower end into which partially extend and open the respective ends of the various pipeline sections and, to provide desired flow between the pipeline sections, a floor is formed in the bottom of the manhole housing cast of cementitious material such as concrete extending to at least approximately half the height of the pipes with a U-shaped trough or troughs, commonly referred to as an invert or inverts, formed in the cementitious material extending as desired between the ends of the pipeline sections. Traditionally, such manhole floors have been formed by pouring a sufficient quantity of the cementitious material into the bottom of the manhole housing and manually working the material by hand troweling throughout substantially the entire time period required for casting of the material, a practice which will readily be recognized to be extremely laborious and time consuming and further at best provides imprecise, albeit functional inverts but in certain cases can produce an invert which is so unacceptably roughly finished that the entire removal and reformation of the manhole floor is required.
As an alternative, various types of molds, forms and forming apparatus have been proposed for disposition in the bottom of a manhole housing extending between the pipeline ends opening therein during the pouring of the cementitious material to mold the material as it sets to form therein the desired invert or trough. Examples of such devices and apparatus are disclosed in U.S. Pat. Nos. 725,098; 4,085,918; and 4,278,229. However, such forms substantially only contemplate and provide for the formation of linear inverts between aligned pipeline sections and angularly-intersecting linear invert sections between angularly-oriented pipeline sections and, in practice, such forms have met with minimal industry acceptance limited primarily to usage in forming "straight through" linear inverts between aligned pipes, it still being widely preferred to hand trowel inverts between angularly oriented pipes to provide an at least roughly curved invert therebetween which is greatly preferred over angularly-intersecting linear invert sections. One type of forming apparatus which has been used successfully to form a generally simulatively curved invert between angularly-oriented pipelines employs one or more forming elements formed as wedge-like angular sections of linear forms which wedge-like sections may be arranged individually, in combination and between straight forms as desired to provide an invert having several linear sections which longitudinally extend progressively angularly to one another in a step-like fashion to generally simulate a longitudinally curved invert. However, to date, no satisfactory form or forming apparatus is known to have been developed to provide for the formation of longitudinally curved inverts.
The present invention affords a much needed improvement in the forming element and forming apparatus of the latter above-described type in providing a workable, easily-usable forming element and forming apparatus which is adapted to selectively form curvilinear inverts of precise transverse and longitudinal compound curvature between angularly-oriented pipeline sections.